Solar polar fields

The development of the solar polar field strength throughout a solar sunspot
cycle can be used to predict the magnitude of the next cycle and the peak of the
current cycle. Polar field reversals typically occur within a year of sunspot
maximum. It is not uncommon for the northern and southern polar fields to have
significant differences in field strength and develop asynchronously over time.
The Wilcox Solar Observatory has been collecting solar polar field data since
1975. Non-filtered data can be viewed in this
plot. Below you will find a
plot where only the filtered (by a 20 nHz lowpass filter) field strength data is
displayed. Vertical lines representing field reversals and sunspot cycle min/max
have been added to increase the potential usefulness of the plot.

The northern polar field changed polarity first in June 2012, then weakened
and was near neutral in March 2014. The southern polar field
reversed in July 2013. During the
previous similar polarity reversal in 1989-1991 the northern polar field
reversed 14 months prior to the southern polar field reversal.

Wilcox Solar Observatory data used in this study was obtained via the web
site http://wso.stanford.edu courtesy of J.T.
Hoeksema.